> That would imply the existence of legal “black markets”.

Why’s that? I don’t follow. How does black markets being defined as illegal imply there are legal ones?

BTW, don’t take my word for it, just look it up.

“A black market, underground economy or shadow economy is a clandestine market or series of transactions that has some aspect of illegality or is characterized by some form of noncompliant behavior with an institutional set of rules. If the rule defines the set of goods and services whose production and distribution is prohibited by law, non-compliance with the rule constitutes a black market trade since the transaction itself is illegal.” https://en.wikipedia.org/wiki/Black_market